Dual capillary tube / heat exchanger in combination with cycle priming for reducing charge migration

ABSTRACT

A refrigerator appliance including a multi-capacity compressor and a refrigerant circuit with two conduits and pressure reducing devices arranged in parallel between an evaporator and a condenser. Refrigerant can flow through one, both or none of the conduits and pressure reducing devices. The appliance also has a heat exchanger in contact with either one pressure reducing device, or one conduit between the pressure reducing device and the valve system. The appliance also includes a controller for priming the compressor above a nominal capacity for a predetermined or calculated duration at the beginning of an ON-cycle.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

This invention was made with government support under Award No.DE-EE0003910, awarded by the U.S. Department of Energy. The governmenthas certain rights in the invention.

FIELD OF THE INVENTION

The present invention relates to refrigeration appliances andrefrigeration methods of operation. More particularly, the inventionrelates to refrigeration configurations and methods to improve systemefficiency by minimizing mal-distribution of refrigerant within thesealed system.

BACKGROUND OF THE INVENTION

Many conventional refrigeration systems used in refrigerator appliances,for example, rely on a sealed configuration allowing refrigerant flowthrough a circuit with a compressor, a condenser, a pressure reductiondevice and an evaporator. When the system is called on to cool arefrigeration compartment in the appliance, the compressor operates toincrease the pressure and temperature of the refrigerant existing in avapor state. The refrigerant vapor then travels through the condenser,where it is condensed into a liquid state at constant pressure andtemperature. The liquid refrigerant then passes through the pressurereduction device, and experiences a significant drop in pressure. Thisresults in evaporation of the refrigerant and a significant decrease inthe temperature of the refrigerant. The refrigerant, now in aliquid/vapor state, passes through the evaporator. There, therefrigerant is typically fully vaporized by warmer air that is passedover the evaporator from the compartment intended to be cooled. Theprocess then repeats as the refrigerant vapor is suctioned back into thecompressor.

In general, conventional refrigeration systems operate at a highefficiency when the refrigerant exiting the condenser is in a completelyliquid state and the refrigerant exiting the evaporator is in acompletely vapor state. These refrigerant conditions are possible duringsteady-state operation of the compressor during a cycle of cooling oneor more refrigeration compartments in the appliance. Compressors used inconventional refrigeration systems are also designed and sized tooperate under a variety of ambient temperature and humidity conditions(e.g., tropical environments), and to properly cool refrigerationcompartments in the appliance under a variety of transient conditions(e.g., a large mass of hot food has been introduced into the appliance).

Consequently, conventional systems rarely operate in a continuous,steady-state mode with high efficiency. At certain times, the systemturns the compressor OFF when cooling of a compartment is not necessary.The system might later turn the compressor back ON when cooling isnecessary because, for example, the temperature in a refrigerationcompartment has exceeded a set point. During these down periods,however, refrigerant will re-distribute in the circuit. Oftenrefrigerant in a liquid state will migrate through the circuit and poolin the evaporator. Consequently, the system will need some period oftime to re-distribute the refrigerant within the circuit upon start-upof the compressor when cooling of a compartment is required. Duringthese periods, the system is operating far below the efficienciesachieved when the refrigerant is in a completely liquid state at theexit of the condenser and completely vapor state at the exit of theevaporator.

Efficiency losses on the order of 5-10% may result from the effects ofrefrigerant migration during compressor OFF cycles in conventionalrefrigeration systems. The refrigerant is often not in an ideal statethroughout the refrigerant circuit during the initial phase of acompressor ON cycle. Moreover, when warm refrigerant has migrated fromthe condenser to the evaporator during a period when the compressor isnot operating, efficiency is lost from heat transfer of the warmerrefrigerant in the evaporator to the refrigeration compartment. The useof heat exchanging members (e.g., suction line heat exchangers andintercoolers) in some refrigeration systems also can exacerbate theproblem. Heat exchangers in contact with the compressor inlet andevaporator inlet lines can improve system efficiency during steady-stateoperation. However, they tend to prolong the effects of refrigerantmigration during compressor OFF cycles by inhibiting the mass flow rateof the refrigerant through the refrigerant circuit upon the initiationof a compressor ON cycle.

Consequently, what is needed is a system that not only maximizessteady-state efficiency, but also has improved efficiency during theinitial phase of a compressor ON cycle. Conventional systems are notdesigned to address refrigerant migration. Indeed, many conventionalsystems exacerbate the problem by employing heat exchanging elementsdesigned to only improve efficiency during steady-state operation of thecompressor.

The refrigerator appliances, and methods associated with operating them,related to this invention address these problems. They allow for thedesign of control logic that considers the location and condition of therefrigerant in the refrigerant circuit. When refrigerant hasdisadvantageously migrated within the circuit during a compressorOFF-cycle, for example, the appliances and methods according to theinvention can operate to improve overall system efficiency. They achievethese gains by taking an unconventional approach to the operation of theappliance during the relatively short, initial phase of a compressor-ONcycle. Very generally, these appliances and associated methods arestructured to allow for operation of the appliance at a sub-optimalthermodynamic efficiency during the beginning of a compressor-ON cycle.The immediate emphasis is on an efficient and speedy re-distribution ofthe refrigerant. Accordingly, the appliance can move into a moreefficient, steady-state operational regime at an earlier time thanconventional systems, thereby improving overall system efficiency.

SUMMARY OF THE INVENTION

One aspect of the present invention is to provide a refrigeratorappliance, including a first refrigeration compartment, a condenser, atleast one evaporator in thermal communication with the firstrefrigeration compartment, a refrigerant, and a multi-capacitycompressor with a maximum capacity, a minimum capacity, and a nominalcapacity. The appliance further includes a refrigerant circuit arrangedto allow flow of the refrigerant between the condenser, each evaporatorand the compressor, wherein the refrigerant circuit includes a primaryand a secondary evaporator conduit arranged in parallel between thecondenser and each evaporator. The appliance also includes a primarypressure reducing device configured within each primary evaporatorconduit and a secondary pressure reducing device configured within eachsecondary evaporator conduit, wherein the primary and the secondarypressure reducing devices are set at different pressure reductionlevels. The appliance additionally includes a valve system configuredwithin the primary and the secondary evaporator conduits, wherein thevalve system is capable of selectively directing or restricting flow ofthe refrigerant through each one, or all, of the evaporator conduitsarranged in parallel between the condenser and each evaporator. Theappliance also includes a heat exchanging member in thermal contact withthe primary evaporator conduits, but not the secondary evaporatorconduits, wherein the thermal contact is either at a location downstreamof the valve system and upstream from the primary pressure reducingdevice or at the primary pressure reducing device. In addition, theappliance has a controller for controlling the valve system and thecompressor to maintain the first refrigeration compartment at any of aplurality of selectable temperatures, wherein the controller isconfigured to distribute the refrigerant in the circuit to effectsubstantial sub-cooling of the refrigerant in the condenser orsuperheating of the refrigerant in each evaporator, upon the initiationof a compressor ON-cycle.

Another aspect of the present invention is to provide a method ofoperating a refrigerator appliance. The refrigerator appliance has arefrigeration compartment, an evaporator in thermal communication withthe refrigeration compartment, a condenser, a refrigerant, a compressor,a refrigerant circuit between the condenser, the evaporator and thecompressor, and a primary and a secondary pressure reducing devicearranged in parallel within the refrigerant circuit between thecondenser and the evaporator. The method includes the step of providinga heat exchanging member in thermal contact with the portion of therefrigerant circuit between the condenser and the evaporator containingthe primary pressure reducing device, but not in thermal contact withthe portion of the circuit containing the secondary pressure reducingdevice. The method also includes the steps of providing the compressorin a multi-capacity configuration with a maximum capacity, minimumcapacity, and a nominal capacity, and providing a valve system in therefrigerant circuit between the condenser and the evaporator. The methodfurther includes the steps of operating the compressor and the valvesystem to cause flow of the refrigerant through the refrigerant circuitto chill the evaporator during a compressor ON-cycle; and operating thevalve system and the compressor to maintain the refrigerationcompartment at any of a plurality of selectable temperatures. The methodadditionally includes the step of operating the valve system and thecompressor to distribute the refrigerant in the circuit to effectsubstantial sub-cooling of the refrigerant in the condenser orsuperheating of the refrigerant in the evaporator, upon the initiationof the compressor ON-cycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a refrigeration circuit diagram depicting a configuration thatincludes a condenser, a compressor, an evaporator, two refrigerationcompartments, two pressure reduction devices arranged in parallelbetween the evaporator and the condenser, and a suction line heatexchanger in thermal contact with one of the pressure reduction devices.

FIG. 2 is a refrigeration circuit diagram depicting a configuration thatincludes a condenser, a compressor, an evaporator, two refrigerationcompartments, two pressure reduction devices arranged in parallelbetween the evaporator and the condenser, and an intercooler in thermalcontact with one of the pressure reduction devices.

FIG. 3 is a refrigeration circuit diagram depicting a configuration thatincludes a condenser, a compressor, two evaporators, two refrigerationcompartments, two pressure reduction devices arranged in parallelbetween each evaporator and the condenser, and two suction line heatexchangers, each in thermal contact with one pressure reduction devicearranged between the condenser and each evaporator.

FIG. 4 is a refrigeration circuit diagram depicting a configuration thatincludes a condenser, a compressor, two evaporators, two refrigerationcompartments, two pressure reduction devices arranged in parallelbetween each evaporator and the condenser, and two intercoolers, each inthermal contact with one pressure reduction device arranged between thecondenser and each evaporator.

FIG. 5A is a partial refrigeration circuit diagram depicting a valvesystem with a three-way valve for directing or restricting flow ofrefrigerant through the pressure reduction devices arranged in parallelbetween a condenser and an evaporator.

FIG. 5B is a partial refrigeration circuit diagram depicting a valvesystem with two, two-way valves for directing or restricting flow ofrefrigerant through the pressure reduction devices arranged in parallelbetween a condenser and an evaporator.

FIG. 6A is a partial refrigeration circuit diagram depicting a valvesystem with three, three-way valves for directing or restricting flow ofrefrigerant through the pressure reduction devices arranged in parallelbetween a condenser and two evaporators.

FIG. 6B is a partial refrigeration circuit diagram depicting a valvesystem with six, two-way valves for directing or restricting flow ofrefrigerant through the pressure reduction devices arranged in parallelbetween a condenser and two evaporators.

FIG. 7 is a refrigeration circuit diagram depicting a configuration thatincludes a condenser, a compressor, an evaporator, two refrigerationcompartments, and a pressure reduction device arranged between theevaporator and the condenser.

FIG. 8 is a refrigeration circuit diagram depicting a configuration thatincludes a condenser, a compressor, two evaporators, two refrigerationcompartments, and a pressure reduction device arranged between eachevaporator and the condenser.

FIG. 9 is a refrigeration circuit diagram depicting a configuration thatincludes a condenser, a compressor, an evaporator, two refrigerationcompartments, a pressure reduction device arranged between theevaporator and the condenser, and a suction line heat exchanger inthermal contact with the pressure reduction device.

FIG. 10 is a refrigeration circuit diagram depicting a configurationthat includes a condenser, a compressor, two evaporators, tworefrigeration compartments, a pressure reduction device arranged betweeneach evaporator and the condenser, and a suction line heat exchanger inthermal contact with each pressure reduction device.

FIG. 11 is a refrigeration circuit diagram depicting a configurationthat includes a condenser, a compressor, an evaporator, tworefrigeration compartments, a pressure reduction device arranged betweenthe evaporator and the condenser, and an intercooler in thermal contactwith a portion of the refrigeration circuit upstream of the pressurereduction device.

FIG. 12 is a refrigeration circuit diagram depicting a configurationthat includes a condenser, a compressor, two evaporators, tworefrigeration compartments, a pressure reduction device arranged betweeneach evaporator and the condenser, and an intercooler in thermal contactwith a portion of the refrigeration circuit upstream of each pressurereduction device.

DETAILED DESCRIPTION

For purposes of description herein, the invention may assume variousalternative orientations, except where expressly specified to thecontrary. Further, the specific devices and processes illustrated in theattached drawings and described in the following specification aresimply exemplary embodiments of the inventive concepts defined in theappended claims. Hence, specific dimensions and other physicalcharacteristics relating to the embodiments disclosed herein are not tobe considered as limiting, unless the claims expressly state otherwise.

FIGS. 1 and 2 each provide a schematic illustrating refrigeratorappliance 10 with a refrigeration circuit and control components.Refrigerant circuit 20 includes a series of conduits allowing flow ofrefrigerant 8 through a compressor 2, condenser 4, pressure reductiondevices 32 and 34, a first evaporator 12 and then back to the compressor2. In particular, compressor 2 supplies refrigerant 8 through compressoroutlet line 30 to condenser 4. A check valve 6 may be placed in thecompressor outlet line 30 to prevent reverse migration of refrigerantback into the compressor 2 during compressor OFF cycles, for example.Refrigerant 8 then flows out of condenser 4 and is presented to valvesystem 36. In the embodiments depicted in FIGS. 1-2, valve system 36 isa three-way valve capable of directing or restricting refrigerant 8 flowthrough secondary evaporator conduit line 22, primary evaporator conduitline 24, or both lines 22 and 24. The evaporator conduit lines 22 and 24in refrigerant circuit 20 merge upstream of evaporator 12, permittingflow of refrigerant 8 into evaporator 12. Refrigerant 8 exits evaporator12 and flows through compressor inlet line 28, thus completingrefrigerant circuit 20.

In the embodiments depicted in FIGS. 1-2 (and others discussed later),valve system 36 can include one or more of the following types ofvalves: solenoid-driven, single inlet and single outlet-type valves;solenoid-driven single inlet and selectable-outlet type valves; andstepper-motor driven single inlet and selectable-outlet type valves.Other types of valves or structures (e.g., manifolds) known in the artare permissible for use in valve system 36 that perform the intendedthree-way function of either line open, both lines open or both linesclosed for the depicted system.

As will also be appreciated by those skilled in the art, refrigerant 8can be composed of any of a number of conventional coolants employed inthe refrigeration industry. For example, refrigerant 8 can be R-134a,R-600a or similar recognized refrigerants for vapor compression systems.

In the embodiments depicted in FIGS. 1 and 2 (and those associated withFIGS. 3 and 4 discussed later), compressor 2 may be a single-speed orsingle-capacity compressor, appropriately sized based on the particularsystem parameters of the refrigerator appliance 10. In addition,compressor 2 may also be a multi-capacity compressor capable ofoperation at any of a finite group of capacities or speeds. Stillfurther, compressor 2 may also be a variable capacity or speedcompressor (e.g., a variable speed, reciprocating compressor operatingfrom 1600 to 4500 rpm or ˜3:1 capacity range) or a linear compressor,capable of operating within a large range of compressor speeds andcapacities.

FIGS. 1 and 2 further depict a refrigerator appliance containing a firstrefrigeration compartment 14 in thermal communication with firstevaporator 12. A first refrigeration compartment fan 16 may be locatedwithin the appliance to direct warm air in compartment 14 over theevaporator 12. Air manifolds or other types of heat exchange enhancementstructures as known in the art may be arranged to facilitate this heattransfer between evaporator 12 and compartment 14. During operation ofthe refrigerant circuit 20, for example, the warmer air in compartment14 flows over evaporator 12 and is cooled by the refrigerant 8 passingthrough evaporator 12.

The refrigerator appliance 10 depicted in FIGS. 1 and 2 also includes asecond refrigeration compartment 15, separated convectively fromrefrigeration compartment 14 by a damper 18. Damper 18 or some othersuitable structure as known in the art may be operated to allow flow ofair cooled by first evaporator 12 to convectively extract heat fromcompartment 15, thereby cooling compartment 15. If fan 16 is used andair flows through damper 18, a return air path is also required (notshown in FIGS. 1 and 2). Return air path structures can be configured asknown in the art. Preferably, first refrigeration compartment 14 ismaintained at a temperature below 0° centigrade and acts as a freezercompartment in the refrigerator appliance. Also preferable is the use ofrefrigeration compartment 15 at a temperature above 0° centigrade as afresh food compartment in the appliance. Other arrangements ofrefrigeration compartments 14 and 15, first evaporator 12, fan 16 anddamper 18 are possible, provided that compartment 14 and 15 remains inthermal contact with evaporator 12.

As shown in FIGS. 1 and 2, secondary pressure reduction device 32 isarranged within secondary evaporator conduit line 22 and primarypressure reduction device 34 is arranged within primary evaporatorconduit line 24. When refrigerant 8 existing in a liquid state flowsthrough either, or both, of the pressure reduction devices 32 and 34, itexperiences a significant pressure and temperature drop. A substantialquantity of refrigerant 8 flashes to a vapor state during flow throughpressure reduction devices 32 and/or 34. Pressure reduction devices 32and 34 may be constructed as capillary tubes, expansion valves, orificerestrictors, needle valves and/or any other suitable structures known inthe art capable of performing the intended function. Furthermore,pressure reduction devices 32 and 34 are each configured to subjectrefrigerant 8 to different pressure reduction levels. Accordingly, therefrigerant 8 that flows through secondary evaporator conduit line 22(after exiting secondary pressure reduction device 32) possesses adifferent temperature and pressure than the refrigerant 8 flowingthrough primary evaporator conduit line 24 (after exiting primarypressure reduction device 34).

As depicted in the FIG. 1 embodiment, the refrigerant circuit 20includes a suction line heat exchanger 26 arranged in thermal contactwith primary pressure reduction device 34. In the embodiment depicted inFIG. 2, the refrigerant circuit 20 includes an intercooler 27 arrangedin thermal contact with the portion of the refrigerant circuit 20downstream of valve system 36 and upstream of primary pressure reductiondevice 34. Further, a portion of refrigerant circuit 20 that exits firstevaporator 12 and drains into compressor inlet line 28 is also arrangedin thermal contact with suction line heat exchanger 26 or intercooler27.

During nominal (e.g., steady-state) operation conditions of therefrigerator appliance 10, refrigerant vapor 8 exiting first evaporator12 flows through heat exchanger 26 or intercooler 27 and exchanges heatwith relatively warmer refrigerant 8 that passes through pressurereduction device 34 toward evaporator 12. This heat exchange occurs whenrefrigerant 8 is permitted to flow through pressure reduction device 34by the valve system 36. Operation of heat exchanger 26 or intercooler 27to warm refrigerant 8 passing back to the compressor 2 and coolrefrigerant 8 that passes through pressure reduction device 34 towardevaporator 12, has the effect of improving the overall thermodynamicefficiency of the appliance during nominal operation conditions.

A controller 40 is also illustrated in FIGS. 1 and 2 for controllingoperation of the refrigerator appliance. In general, controller 40operates the compressor 2 and valve system 36, for example, to maintainrefrigeration compartments 14 and 15 at various, desired temperatures.The controller 40 may also operate a condenser fan 102 configured todirect flow of ambient air over condenser 4 to further assist inefficiently maintaining desired temperatures in the refrigerationcompartments 14 and 15. Preferably, condenser fan 12 is arranged inproximity to or within a housing associated with condenser 4. Inaddition, controller 40 may operate damper 18, first refrigerationcompartment fan 16 and/or check valve 6 to maintain desired temperaturesin refrigeration compartments 14 and 15. Note, however, that checkvalves are typically passive, not requiring electronic activation.Furthermore, controller 40 may be disposed to control and optimize thethermodynamic efficiency of the refrigerator appliance by controlling oradjusting the fan 102, damper 18, fan 16 and/or check valve 6components.

Controller 40 is disposed to receive and generate control signalsthrough wiring arranged between and coupled to compressor 2, valvesystem 36, condenser fan 102, damper 18 and first refrigerationcompartment fan 16. In particular, wiring 42, 46 and 48 are arranged tocouple controller 40 with valve system 36, check valve 6 and compressor2, respectively. Further, wiring 54, 58 and 104 are arranged to couplecontroller 40 with first refrigeration compartment fan 16, damper 18 andcondenser fan 102, respectively.

In the embodiments illustrated in FIGS. 1 and 2, controller 40 alsorelies on refrigeration compartment temperature sensors to perform itsintended function within the refrigerator appliance. Controller 40 iscoupled to sensors 14 a and 15 a arranged in refrigeration compartments14 and 15, respectively, with wiring (not shown in FIGS. 1 and 2).Sensors 14 a and 15 a generate signals indicative of temperature as afunction of time in their respective refrigeration compartments 14 and15 and send this data to controller 40. Thermistors, thermocouples, andother types of temperature sensors known in the art are suitable for useas sensors 14 a and 15 a.

As depicted in FIGS. 1 and 2, controller 40 may also rely on condenserexit sensor assembly 5 and/or evaporator exit sensor assembly 106 toevaluate the condition of the refrigerant 8 within refrigerant circuit20. In particular, sensor assemblies 5 and 106 are configured to measuretemperature and/or pressure of the refrigerant 8 at the exit of thecondenser 4 and first evaporator 12, respectively. Various combinationsof thermistors, thermocouples, and other temperature sensors arepermissible for use in sensor assemblies 5 and 106. Also permissible foruse in sensor assemblies 5 and 106 are transducers, piezoelectricsensors, and other types of pressure sensors known in the art.

In FIGS. 3 and 4, refrigerator appliances 10 are illustrated inschematic form with a refrigeration circuit and control components. Theappliances depicted in these figures each have two evaporators, firstevaporator 12 and second evaporator 52, in contrast to the singleevaporator-configurations shown in FIGS. 1 and 2. Accordingly, there aresome differences in the refrigerant circuit 20 for these embodiments.After the refrigerant 8 exits condenser 4, it is presented to valvesystem 36. Here, valve system 36 consists of two, three-way valves:first evaporator primary valve 38 and second evaporator primary valve39. The valve system 36 can direct or restrict flow of refrigerant 8 toone or both of the first and second evaporators 12 and 52. The types ofvalves suitable for use here are the same as those mentioned earlier inconnection with the valves suitable for use in the appliancesillustrated in FIGS. 1-2.

In turn, first evaporator primary valve 38 can direct or restrict flowof refrigerant 8 through one or both of the primary and secondaryevaporator conduits 24 and 22, respectively, arranged between firstevaporator 12 and valve 38. Thus, refrigerant 8 can flow through eitheror both of conduits 24 and 22 before these conduits merge into a singleinlet into first evaporator 12.

Similarly, the valve system 36 can direct flow of refrigerant 8 tosecond evaporator primary valve 39. Valve 39 can then direct or restrictflow of refrigerant 8 to one or both of primary and secondary evaporatorconduits 64 and 62, respectively, arranged in refrigerant circuit 20between second evaporator 52 and valve 39. Accordingly, refrigerant 8then flows through either or both of conduits 64 and 62 before theseconduits merge into a single inlet into second evaporator 52.

Also depicted in FIGS. 3 and 4 are pressure reduction devices 34 and 32arranged in the two sets of evaporator conduits, conduits 24 and 22,along with conduits 64 and 62. If refrigerant 8 is directed by firstevaporator primary valve 38 through primary evaporator conduit 24, itwill experience a significant pressure drop through primary pressurereduction device 34. Refrigerant 8 that flows through secondaryevaporator conduit 22 will experience a significant pressure dropthrough secondary pressure reduction device 32. Likewise, if refrigerant8 is directed by second evaporator primary valve 39 through primaryevaporator conduit 64, it will experience a significant pressure dropthrough primary pressure reduction device 34 arranged in the sameconduit. Refrigerant 8 that flows through secondary evaporator conduit62 will experience a significant pressure drop through secondarypressure reduction device 32. Pressure reduction devices 32 and 34 maybe capillary tubes, expansion valves, orifice restrictors, needle valvescapable of performing the intended function described in the embodimentsassociated with FIGS. 1 and 2, or any other suitable structures known inthe art.

The FIGS. 3 and 4 embodiments also include heat exchanging membersarranged in the suction line of refrigerant circuit 20 leading back intocompressor inlet line 28. As shown in FIG. 3, suction line heatexchangers 26 and 66 are arranged with the primary evaporator conduits24 and 64 for first evaporator 12 and second evaporator 52,respectively. Further, heat exchangers 26 and 66 are configured to be inthermal contact with pressure reduction devices 34. In FIG. 4,intercoolers 27 and 67 are arranged in the primary evaporator conduits24 and 64 for first evaporator 12 and second evaporator 52,respectively. Intercoolers 27 and 67 are also configured in theseconduits to be in thermal contact with the portion of refrigerantcircuit 20 downstream of valve system 36 and upstream of primarypressure reduction device 34. In addition, a portion of refrigerantcircuit 20 that exits evaporators 12 and 52 and drains into compressorinlet line 28 is configured to be the suction line heat exchanger 26 and66 elements (FIG. 3) or the intercooler 27 and 67 elements (FIG. 4).Also, a check valve 6 is configured in the portion of circuit 20 thatexits first evaporator 12. Check valve 6 prevents back flow ofrefrigerant 8 from the exit of second evaporator 52 into evaporator 12.

As discussed earlier, the embodiments of refrigerator appliance 10depicted in FIGS. 3 and 4 each rely on two evaporators—first evaporator12 and second evaporator 52. First evaporator 12 is arranged in thermalcommunication with first refrigeration compartment 14. Firstrefrigerator compartment fan 16 is arranged in the appliance to directwarm air in compartment 14 over evaporator 12. When compressor 2 isoperating and refrigerant 8 is flowing through refrigerant circuit 20,for example, the warm air in compartment 14 may be directed over firstevaporator 12 by operation of fan 16. Flow of refrigerant 8 throughevaporator 12 cools the warm air in compartment 14 by this operation.

Second evaporator 52 is in thermal communication with secondrefrigeration compartment 15. Here, second refrigeration compartment fan17 is arranged in the appliance to direct warm air in compartment 15over second evaporator 52. During operation of the appliance andcompartment fan 17, for example, refrigerant 8 may flow throughrefrigerant circuit 20 and be directed through evaporator 52. The warmair in second refrigeration compartment 15 that is directed overevaporator 52 by fan 17 is then cooled by the refrigerant 8 flowingthrough evaporator 52.

The controller 40, wiring and sensors configured in the refrigeratorappliances depicted in FIGS. 3 and 4 are generally the same as thosediscussed for the embodiments depicted in FIGS. 1 and 2. However,controller 40 is also coupled to receive individual control wiring 42elements for first and second evaporator primary valves 38 and 39 forpurposes of controlling cooling operations associated with theappliance. In addition, wiring 56 is coupled to controller 40 and secondrefrigeration compartment fan 17 to allow controller 40 to operate andcontrol fan 17. Controller 40 is also coupled via wiring 46 to a secondcheck valve 6 that is arranged in the portion of refrigerant circuit 20that exits first evaporator 12.

Controller 40 can evaluate the condition of refrigerant 8 in the FIGS. 3and 4 embodiments by evaluating temperature and/or pressure signals as afunction of time from condenser exit sensor assembly 5 and/or firstevaporator exit sensor assembly 106. Sensor assemblies 5 and 106 operateand function together with controller 40 in the same manner as discussedearlier in connection with the embodiments associated with FIGS. 1 and2. Furthermore, the controller 40 in the dual-evaporator configurationdepicted in FIGS. 3 and 4 may evaluate the temperature and/or pressuresignals received from second evaporator exit sensor assembly 108 thatare associated with the condition of refrigerant 8 at that location.Sensor assemblies 5, 106 and 108 may be constructed from the same typesof temperature and pressure sensors described earlier for the FIGS. 1and 2 embodiments.

The embodiments of refrigerator appliance 10 in FIGS. 1-4 can each beoperated in a similar manner to efficiently cool refrigerationcompartments 14 and/or 15 to maintain the temperature in the respectivecompartments at various, desired temperatures. Controller 40 activatescompressor 2 and valve system 36 to cause flow of refrigerant 8 throughrefrigerant circuit 20 to chill evaporators 12 and/or 52 during acompressor-ON cycle. For example, refrigerant 8 is generally compressedin a vapor state to a higher temperature in compressor 2. Upon enteringcondenser 4, refrigerant 8 is cooled by the removal of heat at aconstant pressure and condenses to a liquid state. Refrigerant 8 is thendirected through the valve system 36 and through the pressure reductiondevices 32 and/or 34. As refrigerant 8 passes the pressure reductiondevices 32 and/or 34, it experiences a significant pressure drop. Muchof the refrigerant vaporizes and the temperature of the refrigerant 8vapor/liquid mixture is decreased. Refrigerant 8 then enters one or moreof the evaporators 12 and 52, and typically is completely vaporized bythe passage of warm air from compartments 14 and/or 15. Refrigerant 8then travels back through compressor inlet line 28 into compressor 2 tobegin the cycle again through refrigerant circuit 20.

At the very beginning of the compressor-ON cycle, first evaporator 12and/or 52 each may contain above-optimal quantities of refrigerant 8. Ifthe systems depicted in FIGS. 1-4 were operated in a conventionalfashion by directing refrigerant 8 through heat exchanging members 26,66, 27 and/or 67 during the initial phase of a compressor ON-cycle, asubstantial duration of this period would be devoted to theredistribution of refrigerant 8 within refrigerant circuit 20 until itreaches a near-nominal equilibrium state. Thermodynamic efficiencies,however, are optimal once the refrigerant 8 is within a nominalequilibrium state within refrigerant circuit 20.

Accordingly, the refrigerator appliances 10 described in FIGS. 1-4 areconfigured to bypass the heat exchanging members 26, 66, 27 and 67during the initial phase of a compressor-ON cycle. While it is typicallymore efficient to operate these appliances by directing refrigerantthrough the heat exchanging members (e.g., suction line heat exchangersor intercoolers) during steady-state operation, these appliances havethe unique ability of operating differently during the initial phase ofa compressor ON-cycle. Higher mass flow rates of refrigerant 8 withinrefrigerant circuit 20 are possible when the heat exchanging members arebypassed. In FIG. 1, for example, controller 40 directs refrigerant 8through main valve assembly 36 into secondary evaporator conduit 22 andpressure reduction device 32. This effectively bypasses heat exchangingmember 26. Similarly, in FIG. 3, heat exchanging members 26 and 66 arebypassed by the selective flow of refrigerant 8 by first and secondevaporator primary valves 38 and 39 through secondary evaporatorconduits 22 and 62, respectively. In this manner, the quantities ofrefrigerant 8 that have pooled in evaporators 12 and/or 52 duringcompressor-OFF cycles can be quickly re-distributed within refrigerantcircuit 20 into a nominal equilibrium state during the initial phase ofa compressor ON-cycle.

After refrigerant 8 has reached a near-nominal equilibrium state withinrefrigerant circuit 20, controller 40 then switches the flow ofrefrigerant 8 back through evaporator conduits (e.g., conduits 24 and/or64) in thermal contact with the heat exchanging members. This operationensures optimal thermodynamic efficiency during steady-state operation.In FIGS. 1 and 2, for example, controller 40 operates valve system 36 todirect flow of refrigerant 8 through primary evaporator conduit 24.Consequently, refrigerant 8 passes through pressure reduction device 34,which is in thermal contact with heat exchanging member 26 (FIG. 1) orthrough conduit 24 in thermal contact with intercooler 27 (FIG. 2).Controller 40 operates the embodiments shown in FIGS. 3 and 4 in asimilar fashion and directs refrigerant 8 through first and secondevaporator primary valves 38 and 39 into primary evaporator conduits 24and 64. This has the effect of directing refrigerant 8 through suctionline heat exchangers 26 and 66 (FIG. 3) or intercoolers 27 and 67 (FIG.4).

The length of time that controller 40 directs refrigerant 8 to bypassheat exchanging members 26, 27, 66 and/or 67 during the initial phase ofa compressor-ON cycle can be pre-determined or calculated as a variable.In the former case, the duration can be predetermined (e.g., set as afixed parameter) based on various system geometries and configurations.In particular, the duration of the heat exchanging member bypass maydepend on the quantity of refrigerant in circuit 20, the length andgeometry of circuit 20, the size of compressor 2, condenser 4,evaporators 12 and 52, the materials used to fabricate these components,and other factors. In addition, the dynamics of the distribution ofrefrigerant 8 in the refrigerant circuit 20 depicted in FIGS. 1-4 can bemodeled and understood through techniques and measurements as known inthe art. Accordingly, the length of time that controller 40 bypasses theheat exchanging elements can be set at one or more values. Multiplesettings, for example, may be needed to take into account differentdegrees of refrigerant migration. The degree of migration may be afunction of the length and/or frequency of the compressor OFF-cycles andthe current refrigerant 8 condition as evaluated by controller 40 basedon inputs from sensor assemblies 5, 106 and 108. Alternatively, theduration of the bypass can be set to a fixed period (e.g., 120 seconds)after the beginning of a compressor-ON cycle, or it may be set for aprescribed time (e.g., 45 minutes) after the power cord of the appliancehas been plugged into a power outlet after a significant down period.

Controller 40 may also operate to direct refrigerant 8 to bypass theheat exchanging members 26, 27, 66 and/or 67 depicted in FIGS. 1-4 for aduration that is calculated (e.g., at various times or continuously)based at least on an evaluation of the condition of refrigerant 8. Asdiscussed earlier, controller 40 can ascertain the condition ofrefrigerant 8 by evaluating the temperature and/or pressure signalsreceived from condenser exit assembly 5 and/or evaporator exitassemblies 106 (FIGS. 1-4) and 108 (FIGS. 3-4). For example, there isequilibrium of refrigerant 8 within circuit 20 when refrigerant 8 existsin a substantially liquid state at the exit of condenser 4 (i.e., LiquidLine Sub-cooling). Similarly, there is also equilibrium in circuit 20when refrigerant 8 is in a substantially vapor state at the exit ofevaporator 12 and evaporator 52, if present. Ideally, refrigerant 8exists in a superheated, vapor state (0-4° centigrade beyond thecorresponding saturation temperature for the particular refrigerantpressure) at the evaporator exit.

Thus, controller 40 can evaluate whether the Liquid Line Sub-coolingand/or

Evaporator Exit Superheat conditions exist for refrigerant 8. Whencontroller 40 detects these conditions through readings from sensorassemblies 5, 106 and /or 108, it can operate the valve system 36 tostop the heat exchanger bypass operation and direct refrigerant 8 backthrough conduits in thermal contact with the heat exchanging elementswithin refrigerant circuit 20.

Controller 40 may also assess whether there are Liquid Line Sub-coolingand/or Evaporator Exit Superheat conditions by evaluating thetemperatures of refrigeration compartments 14 and 15 (if applicable).Through prior modeling and experimental work (e.g., direct measurementsof refrigerant temperature and pressure), it is possible to predictLiquid Line Sub-cooling and/or Evaporator Exit Superheat conditionsbased on actual temperature measurements in the compartments as afunction of time. Another related approach is for controller 40 to ceasethe heat exchanger bypass operation at the point in which thetemperature (warm-up) decay rate in compartments 14 and/or 15 approacheszero, signifying that an effective compartment cooling operation hasbegun.

In addition, controller 40 may rely on another approach to determine thetiming of Liquid Line Sub-cooling and/or Evaporator Exit Superheatconditions for refrigerant 8 within circuit 20. This approach relies ondata associated with operation of compressor 2. When compressor 2 isconfigured as a linear compressor, controller 40 can evaluate theresonant frequency of the piston within the compressor as a function oftime. Through experimentation and modeling, the piston frequencyresponse for compressor 2 and/or the derivative of the frequencyresponse can be correlated to the temperature and pressure condition ofrefrigerant 8 at the exit of condenser 4 and/or the exit of the firstand second evaporator 12 and 52. Using this data, it is possible tocorrelate compressor piston frequencies to the desired Liquid LineSub-cooling and/or Evaporator Exit Superheat conditions for refrigerant8. These frequencies can then be used to establish a predeterminedduration for the heat exchanger bypass step. Alternatively, controller40 can evaluate the real-time piston frequency of compressor 2 (e.g., byusing vibration sensors coupled to compressor 2 and control wiringcoupled to controller 40 as known in the art). It can then calculate theduration of the heat exchanger bypass step based on the prior-developedfrequency correlations to the Liquid Line Sub-cooling and/or EvaporatorExit Superheat conditions observed in connection with refrigerant 8.

For refrigerator appliances 10 configured with a general, variable speedor variable capacity compressor (not a linear compressor), it is alsopossible for controller 40 to evaluate Liquid Line Sub-cooling and/orEvaporator Exit Superheat conditions for refrigerant 8. Here, controller40 can ascertain the power consumption of compressor 2 as a function oftime and/or the derivative of this power consumption. Prior correlations(based on modeling and experimentation as known in the art) ofcompressor power and/or derivatives of the power to the desiredrefrigerant 8 conditions (e.g., sub-cooling of the refrigerant 8 at thecondenser exit) can be used to set the duration of the heat exchangerbypass step. Preferably, the duration for the bypass step is calculatedin real-time by controller 40 based on the power consumption ofcompressor 2 as a function of time. Some prescribed time (e.g., a fewseconds) after the compressor power consumption has peaked is usually anappropriate time to arrest the heat exchanging bypass step. This isbecause the peak of the compressor power consumption can generally becorrelated to the time in which most of refrigerant 8 has reached asub-cooled state at the exit of the condenser and/or a superheatcondition exists at the evaporator exit. Also note that the aboveapproach to setting the duration of the heat exchanger bypass based oncompressor power consumption can be employed when compressor 2 isconfigured as a linear compressor.

The refrigerator appliances 10 depicted in FIGS. 1-4 can also beoperated by controller 40 to manage temperature control of refrigerationcompartments 14 and 15 during transient conditions. Various situationsmay arise during operation of these refrigerator appliances that requiremaximum or higher-than-nominal cooling rates in compartments 14 and 15to maintain desired temperatures in these compartments. For example, adoor to compartment 14 or 15 may be inadvertently left open for a longduration, substantially warming the affected compartment. Similarly, alarge quantity of hot food may be introduced into compartment 14 or 15,causing an appreciable rise in compartment temperature. To address thesetransient conditions, and others, controller 40 may direct flow ofrefrigerant 8 through both pressure reduction devices 32 and 34 at thesame time. This maximizes flow rates to evaporators 12 and 52, therebyimparting significant cooling rates to refrigeration compartments 14 and15.

Controller 40 may also operate the refrigerator appliances 10 depictedin FIGS. 1-4 in another manner to further address sub-optimaldistribution of refrigerant 8 in circuit 20. Right before controller 40activates compressor 2 at the beginning of a compressor-ON cycle,controller 40 may engage valve system 36 to allow the refrigerant 8 toequalize in pressure within circuit 20. In particular, controller 40operates valve system 36 to allow pressure equalization and flow ofrefrigerant 8 into evaporator conduits 22, 24, 62 and/or 64 (see FIGS.1-4). This operation also has the effect of promoting betterdistribution of refrigerant 8 in circuit 20, potentially reducing thetime necessary to run the appliance in the mode where the heatexchanging members are bypassed.

Controller 40 can impart further efficiency gains by operating therefrigerator appliances 10 depicted in FIGS. 1-4 according to certainprocedures at the end of a compressor ON-cycle. For example, controller40 can engage valve system 36 to restrict flow of refrigerant 8 throughevaporator conduits 22 and 24 (FIGS. 1-4), 62 and/or 64 (FIGS. 3-4) andpressure reduction devices 32 and 34 (FIGS. 1-4) at the end of asteady-state compressor-ON cycle. This has the effect of preventing orminimizing the pooling of refrigerant 8 in a liquid state withinevaporators 12 and/or 52.

Still further, controller 40 can obtain further thermodynamicefficiencies by operating condenser fan 102 and/or refrigerationcompartment fans 16 and 17 at the end of a compressor-ON cycle.Operation of condenser fan 102 serves to further cool refrigerant 8 thatexists in a high temperature state upon return to compressor 2 frominlet line 28 and flow into condenser 4. Similarly, the continued shortterm operation of refrigeration fans 16 and 17 can further extractcooling from the cold, evaporator 12 and/or evaporator 52, even afterthe compressor 2 is switched OFF during operation.

FIGS. 5A and 5B depict embodiments of valve system (e.g., valve system36) configurations that may be used in the single-evaporator,refrigerator appliances 10 shown in FIGS. 1-2, for example. In FIG. 5A,three-way valve assembly 70 comprises one three-way valve 78 configuredto direct or restrict flow of refrigerant 8 (from condenser 4) throughprimary evaporator conduit 76 and/or secondary evaporator conduit 74 andpressure reduction devices 34 and 32, respectively. Refrigerant 8 thenflows into first evaporator 12. Although the remainder of refrigerantcircuit 20 is not shown in FIG. 5A, it is to be understood thatrefrigerant 8 flows back through heat exchanger 26 or intercooler 27(not shown) on the way back to compressor 2. Also not shown in FIG. 5Ais controller 40, which is coupled to valve 78 for purposes ofcontrolling the flow of refrigerant 8 through the evaporator conduits 74and 76.

For its part, FIG. 5B depicts a dual, one-way valve assembly 80 foraccomplishing the same function as valve assembly 70 in FIG. 5A. Here,three-way valve 78 is replaced with two, one-way valves 88. One, one-wayvalve 88 is configured for primary evaporator conduit 76 and one,one-way valve 88 is configured for secondary evaporator conduit 74. Inall other respects, the configuration for valve assembly 80 in FIG. 5Bis identical to the valve assembly 70 configuration depicted in FIG. 5A.Here, controller 40 can also operate either or both of one-way valves 88to direct or restrict flow of refrigerant 8 through the evaporatorconduits 74 and 76.

FIGS. 6A and 6B depict various embodiments of valve system (e.g., valvesystem 36) configurations that may be employed in the dual-evaporator,refrigerator appliance embodiments illustrated in FIGS. 3-4. In FIG. 6A,the dual-evaporator refrigerator appliance 10 relies on a valve assembly96 comprised of two, three-way valves 78 configured to direct orrestrict flow of refrigerant 8 through the two sets of evaporatorconduits 74 and 76 arranged between first evaporator 12 and condenser 4,and second evaporator 52 and condenser 4. Although not illustrated inFIG. 6A, a controller 40 coupled to each valve 78 can effectively director restrict flow of refrigerant 8 through each of the evaporatorconduits arranged in refrigerant circuit 20 between evaporators 12 and52, and condenser 4.

In FIG. 6B, valve assembly 98 relies on four, one-way valves 88 as areplacement for the two, three-way valves depicted in FIG. 6A. Again, inall other respects, the configuration for valve assembly 98 in FIG. 6Bhas the identical function as the valve assembly 96 depicted in FIG. 6A.

Valve systems and assemblies that properly function with therefrigerator appliances 10 depicted in FIGS. 1-4 are not exclusive tothose discussed earlier and illustrated in FIGS. 5A, 5B, 6A and 6B.Various combinations of one-way and three-way valves of various types(e.g., valve 78, valve 88) can be employed in the evaporator conduitswithin these single- and dual-evaporator refrigerator appliances.Although not depicted in FIGS. 5A-6B, two-way valves may also beemployed in these valve systems and assemblies. These valves can director redirect flow of refrigerant 8 through either one of two outlets. Forexample, two-way valves 38 a and 39 a may be configured in thearrangement shown in FIG. 3 as replacements for three-way valves 38 and39 (or as replacements for valves 78 in FIG. 6A) along with oneadditional two-way valve positioned upstream of the 38 a and 39 atwo-way valves and downstream from condenser 4. Preferably, controller40 should be capable of controlling the valve combination to direct orrestrict flow of refrigerant 8 through the evaporator conduits arrangedin refrigerant circuit 20 between each evaporator (e.g., firstevaporator 12, and second evaporator 52) and the condenser 4.

Other variants of the single- and dual-evaporator refrigerator appliance10 and methods illustrated and discussed in connection with FIGS. 1-4are viable. For example, refrigerator configurations with only onerefrigeration compartment, e.g., compartment 14, are suitable for highefficiency operation according to the invention, including the heatexchanging member bypass operation discussed above. For theseappliances, at least one evaporator 12 should be arranged in thermalcommunication with the compartment 14. As another example, amulti-evaporator/refrigerator appliance 10 can employ a multi-inlet typecompressor for the compressor 2 element. In this scenario, each inlet ofcompressor 2 requires a dedicated suction line from each evaporatorarranged in refrigerator appliance 10.

Various refrigerator appliance configurations with single or multipleevaporators are also possible. However, at least two evaporator conduits(e.g., 22 and 24) and at least two pressure reduction devices (e.g., 32and 34) should be configured in parallel in refrigerant circuit 20between each evaporator associated with the appliance and the condenser4. Thus, a set of two or more evaporator conduits should be configuredin parallel within refrigerant circuit 20 and arranged such that the setis associated with one evaporator. Another set of evaporator conduitsshould be arranged for the next evaporator arranged in the appliance,and so on. In addition, a heat exchanging element (e.g., suction lineheat exchanger 26, intercooler 27, etc.) should be arranged in thermalcontact with one, but not all of, the evaporator conduits downstream ofthe valve system 36 arranged between each evaporator and the condenser.Alternatively, the heat exchanging member can be placed in thermalcontact with one, but not all of, the pressure reduction devices.

The refrigerator appliance 10 embodiments depicted in FIGS. 7-12 rely ona different approach to maximizing overall thermodynamic efficiency.Like the embodiments depicted in FIGS. 1-4, these configurations andassociated methods are structured to evaluate and control thedistribution of refrigerant 8 within refrigerant circuit 20 at thebeginning of a compressor-ON cycle. Instead of directing refrigerant 8to bypass the heat exchanging members within the circuit, the appliancesillustrated in FIGS. 7-12 make use of a high-speed or high-capacitycompressor operation to prime or displace the refrigerant 8 back into anequilibrium state within the circuit. Accordingly, compressor 2 cannotbe configured as a single-speed or single-capacity compressor. Rather,compressor 2 is configured as a multi-capacity compressor capable ofoperation at multiple, finite capacities or speeds; a variable capacityor speed compressor, capable of operation within a spectrum ofcapacities or speeds (e.g., variable speed compressor operating fromapproximately 1600 to 4500 rpm); or a linear compressor also capable ofoperating within a spectrum of speeds and capacities (e.g., an Embraco(Whirlpool SA) Britten compressor operating at 30 to 160 W). Further,compressor 2 should be capable of operation at maximum (e.g., near 4500rpm), minimum (e.g., near 1600 rpm) and nominal capacity levels, amongother settings. In general, the nominal capacity of compressor 2 isabout 35% of the difference between its maximum and minimum capacitylevels (e.g., 0.35*(4500−1600 rpm)=˜1015 rpm).

In large part, the single-evaporator refrigerator appliance embodimentsdepicted in FIGS. 7, 9, and 11 are similar to the embodimentsillustrated in FIGS. 1 and 3. There is one significant difference,however. Only one conduit, primary evaporator conduit 24, is arrangedbetween condenser 4 and first evaporator 12. Accordingly, only onepressure reduction device 34 is configured within refrigerant circuit 20between first evaporator 12 and condenser 4. Since valve system 36 onlyneeds to direct or restrict flow of refrigerant 8 from condenser 4through pressure reduction device 34 (and evaporator conduit 24), it canrely on one, one-way valve (e.g., a valve equivalent to valve 88 in FIG.5B). Other types of valves as known in the art may also be used,provided that they serve the prescribed function.

The refrigerator appliance 10 illustrated in FIG. 7 differs from theembodiments shown in FIGS. 1 and 3 in one other respect. Here, theappliance has no heat exchanging element (e.g., heat exchanger 26 orintercooler 27) arranged within refrigerant circuit 20. Consequently,the drain line from first evaporator 12 directly feeds into compressorinlet line 28 with no thermal contact with primary evaporator conduit 24or pressure reduction device 34. Note, however, that the refrigeratorappliances 10 depicted in FIGS. 9 and 11 do possess a suction line heatexchanger 26 or an intercooler 27, respectively, and these heatexchanging elements and associated conduits are arranged similar totheir counterparts depicted in FIGS. 1 and 3.

Likewise, the dual-evaporator refrigerator appliance embodimentsdepicted in FIGS. 8, 10 and 12 are similar to the embodiments shown inFIGS. 2 and 4. Again, there is one significant difference. Only oneconduit, primary evaporator conduit 24 or 64, is arranged betweencondenser 4 and each evaporator (i.e., evaporators 12 and 52). Hence,there is one primary evaporator conduit 24 associated with the portionof circuit 20 between first evaporator 12 and condenser 4, and oneprimary evaporator conduit 64 arranged between condenser 4 and secondevaporator 52. Accordingly, there is only one pressure reduction device34 configured within refrigerant circuit 20 between first evaporator 12and condenser 4, and one other pressure reduction device 34 betweensecond evaporator 52 and condenser 4.

Since valve system 36 only needs to direct or restrict flow ofrefrigerant 8 from condenser 4 through one, or both of the pressurereduction devices 34, it can rely on one, three-way valve (e.g., athree-way valve comparable to valve 78 in FIG. 5A). Other types ofvalves as known in the art may also be used, provided that they servethe same function.

The refrigerator appliance 10 illustrated in FIG. 8 differs from theembodiments shown in FIGS. 2 and 4 in one other respect. This appliancehas no heat exchanging element (e.g., heat exchanger 26 or intercooler27) arranged within refrigerant circuit 20 associated with either firstevaporator 12 or second evaporator 52. Consequently, the drain linesfrom evaporator 12 and second evaporator 52 directly feed intocompressor inlet line 28 and have no thermal contact with primaryevaporator conduits 24 and 64, or pressure reduction devices 34. Noteagain, however, that the refrigerator appliances depicted in FIGS. 10and 12 possess suction line heat exchangers 26 or intercoolers 27,respectively, and that these heat exchanging elements and associatedconduits are arranged similar to their counterparts depicted in FIGS. 2and 4.

The refrigerator appliances 10 illustrated in FIGS. 7-12 can be operatedduring nominal conditions in virtually the same manner as those detailedfor the appliances shown in FIGS. 1-4. For example, each of theseappliances rely on controller 40 to operate, adjust and controlcompressor 2, check valve(s) 6, valve system 36, first refrigerationcompartment fan 16, second refrigeration compartment fan 17, damper 18and/or condenser fan 102 to maintain the temperature in refrigerationcompartments 14 and 15 at desired levels.

The appliances 10 depicted in FIGS. 7-12, however, take a differentapproach to driving refrigerant 8 into an equilibrium state withinrefrigerant circuit 20 during the initial phase of a compressor-ONcycle. As noted earlier, these appliances do not have secondaryevaporator conduits 22 and 62 to bypass the heat exchanging elements 26,27, 66 and/or 67 arranged within the refrigerant circuit 20. Instead,controller 40 operates the compressor 2 at a priming capacity or speedabove the nominal capacity level (or speed) for a priming duration thatis predetermined or calculated as a variable. The duration of this step,whether predetermined or calculated as a variable, depends on the sameLiquid Line Sub-cooling and Evaporator Exit Superheat criteria outlinedearlier in connection with the appliances depicted in FIGS. 1-4.

Preferably, controller 40 operates compressor 2 at a capacity level wellabove the nominal capacity, which is roughly defined as 35% of thedifference between the maximum and minimum capacity levels of thecompressor (e.g., 0.35*(4500−1600 rpm)=˜1015 rpm). Similar to the heatexchanging bypass operation detailed for the embodiments shown in FIGS.1-4, the compressor priming operation has the effect of re-distributingrefrigerant 8 at a high mass flow rate within circuit 20. Refrigerant 8that has pooled in first evaporator 12 and/or second evaporator 52during compressor-OFF cycles is quickly forced closer to an equilibriumstate within refrigerant circuit 20 during the priming operation.

Controller 40 can thus generate an effective re-distribution ofrefrigerant 8 with various above-nominal compressor speeds andcapacities. Optimal priming speeds and capacity levels, for example, candepend on some of the same appliance features that drive the appropriateduration of the priming step. For example, the overall length of circuit20, the quantity of refrigerant 8 used in circuit 20, the size ofcompressor 2, and other factors can affect the determination of theappropriate compressor priming capacity or speed.

Also note that the priming operation itself is not highly efficient(e.g., high, inefficient compressor power levels are needed to executethe step). But any loss in efficiency associated with the priming stepis offset by the overall gain in thermodynamic efficiency. This isbecause the priming step moves refrigerant 8 into an equilibrium statewithin circuit 20 (i.e., a state where thermodynamic efficiency is high)in significantly less time than conventionally arranged refrigeratorappliances can do so.

Other variants of the refrigerator appliances and associated methods ofoperation in connection with FIGS. 1-4 and 7-12 are possible. Forexample, the configurations of refrigerator appliance 10 associated withFIGS. 1-4 can be operated by controller 40 to re-distribute refrigerant8 within circuit 20 to achieve the Liquid Line Sub-cooling and/orEvaporator Exit Superheat conditions using a combined approach. That is,controller 40 can distribute refrigerant 8 using a combination ofpriming the compressor at higher-than-nominal capacities or speeds,along with bypassing the heat exchanging member(s). Controller 40 canengage in this combined approach upon the initiation of a compressorON-cycle for a duration that is predetermined or calculated as avariable. Further, controller 40 can rely on substantially the samecriteria as discussed earlier in connection with the FIGS. 1-4 and 7-12embodiments to set the duration of these operations.

The refrigerator appliances that operate upon the initiation of acompressor ON-cycle with a combined, compressor priming/heat exchangerbypass approach arrange compressor 2 as a multi-capacity compressor.Further, these appliances have dual evaporator inlet conduits configuredin parallel between the evaporator (e.g., evaporator 12 as shown inFIG. 1) and the condenser 4. The evaporator conduits 22 and 24 depictedin FIG. 1 offer an example of this basic configuration. These appliancesalso have a heat exchanging member, such as suction line heat exchanger26, in thermal contact with only one of the evaporator conduits betweenthe condenser 4 and the evaporator 12 (e.g., see FIG. 1).

It is to be understood that variations and modifications can be made onthe aforementioned structure without departing from the concepts of thepresent invention, and further it is to be understood that such conceptsare intended to be covered by the following claims unless these claimsby their language expressly state otherwise.

We claim:
 1. A refrigerator appliance, comprising: a first refrigerationcompartment; a condenser; at least one evaporator in thermalcommunication with the first refrigeration compartment; a refrigerant; amulti-capacity compressor with a maximum capacity, a minimum capacity,and a nominal capacity; a refrigerant circuit arranged to allow flow ofthe refrigerant between the condenser, the at least one evaporator andthe compressor, the refrigerant circuit comprising a primary and asecondary evaporator conduit arranged in parallel between the condenserand the at least one evaporator; a primary pressure reducing deviceconfigured within the primary evaporator conduit and a secondarypressure reducing device configured within the secondary evaporatorconduit, the primary and the secondary pressure reducing devices set atdifferent pressure reduction levels; a valve system configured withinthe primary and the secondary evaporator conduits, the valve systemcapable of selectively directing or restricting flow of the refrigerantthrough one, or all, of the evaporator conduits arranged in parallelbetween the condenser and the at least one evaporator; a suction lineheat exchanger in thermal contact with the primary evaporator conduit,but not the secondary evaporator conduit, wherein the thermal contact iseither at a location downstream of the valve system and upstream fromthe primary pressure reducing device or at the primary pressure reducingdevice further wherein the suction line heat exchanger is configured totransfer heat to the refrigerant circuit down-stream of the evaporator;and a controller for controlling the valve system and the compressor tomaintain the first refrigeration compartment at any of a plurality ofselectable temperatures, wherein the controller is configured todistribute the refrigerant in the circuit to effect substantialsub-cooling of the refrigerant in the condenser or superheating of therefrigerant in the at least one evaporator, upon the initiation of acompressor ON-cycle, further wherein the controller is configured todirect the refrigerant through the secondary evaporator conduit tobypass the suction line heat exchanger upon the initiation of thecompressor ON-cycle and the primary and secondary evaporator conduitsmerge upstream of the at least one evaporator.
 2. A refrigeratorappliance according to claim 1, wherein the controller is furtherconfigured to operate the multi-capacity compressor at a primingcapacity above the nominal capacity upon the initiation of a compressorON-cycle.
 3. A refrigerator appliance according to claim 2, wherein thenominal capacity is approximately 35% of the difference between themaximum and the minimum capacity of the multi-capacity compressor.
 4. Arefrigerator appliance according to claim 1, wherein the controller isfurther configured to operate the multi-capacity compressor at thepriming capacity and direct the refrigerant through the secondaryevaporator conduit for a duration that is predetermined or calculated.5. A refrigerator appliance according to claim 1, wherein the primaryand secondary pressure reducing devices are selected from the groupconsisting of capillary tubes, expansion valves, orifice restrictors andneedle valves.
 6. A refrigerator appliance according to claim 1, whereinthe valve system comprises a valve or valves selected from the groupconsisting of a solenoid driven single inlet and single outlet-typevalve, a solenoid driven single inlet and at least one selectableoutlet-type valve, and a stepper motor driven single inlet and at leastone selectable output-type valve.
 7. A refrigerator appliance accordingto claim 1, wherein the multi-capacity compressor is selected from thegroup consisting of a variable speed compressor, a variable capacitycompressor, a linear compressor and a two-speed compressor.
 8. Arefrigerator appliance according to claim 1, wherein the suction lineheat exchanger is an intercooler that is in thermal contact with theprimary evaporator conduit, but not the secondary evaporator conduit, ata location downstream from the valve system and upstream from theprimary pressure reducing device.
 9. A refrigerator appliance accordingto claim 1, wherein the suction line heat exchanger is in thermalcontact with the primary pressure reducing device, but not the secondarypressure reducing device.
 10. A method of operating a refrigeratorappliance, the refrigerator appliance having a refrigerationcompartment, an evaporator in thermal communication with therefrigeration compartment, a condenser, a refrigerant, a compressor, arefrigerant circuit between the condenser, the evaporator and thecompressor, and a primary and a secondary pressure reducing devicearranged in parallel within the refrigerant circuit between thecondenser and the evaporator, comprising the steps: providing a suctionline heat exchanger in thermal contact with the portion of therefrigerant circuit between the condenser and the evaporator containingthe primary pressure reducing device, but not in thermal contact withthe portion of the circuit containing the secondary pressure reducingdevice; transferring heat through the suction line heat exchanger fromthe portion of the refrigerant circuit between the condenser and theevaporator to a portion of the refrigerant circuit between theevaporator and compressor; providing the compressor in a multi-capacityconfiguration with a maximum capacity, minimum capacity, and a nominalcapacity; providing a valve system in the refrigerant circuit betweenthe condenser and the evaporator; operating the compressor and the valvesystem to cause flow of the refrigerant through the refrigerant circuitto chill the evaporator during a compressor ON-cycle; directing therefrigerant through the secondary pressure reducing device to bypass thesuction line heat exchanger upon the initiation of the compressorON-cycle, wherein the secondary pressure reducing device lacks a heattransfer member; operating the valve system and the compressor tomaintain the refrigeration compartment at any of a plurality ofselectable temperatures; and operating the valve system and thecompressor to distribute the refrigerant in the circuit to effectsubstantial sub-cooling of the refrigerant in the condenser orsuperheating of the refrigerant in the evaporator, upon the initiationof the compressor ON-cycle.
 11. The method of operating the refrigeratorappliance according to claim 10, wherein the step of operating the valvesystem and the compressor to distribute the refrigerant in the circuitincludes operating the multi-capacity compressor at a priming capacityabove the nominal capacity upon the initiation of the compressorON-cycle.
 12. The method of operating the refrigerator applianceaccording to claim 11, wherein the nominal capacity is approximately 35%of the difference between the maximum and the minimum capacity of themulti-capacity compressor.
 13. The method of operating the refrigeratorappliance according to claim 10, wherein the step of operating the valvesystem and the compressor to distribute the refrigerant in the circuitcontinues for a duration that is predetermined or calculated upon theinitiation of the compressor ON-cycle.
 14. The method of operating therefrigerator appliance according to claim 10, wherein the primary andsecondary pressure reducing devices are selected from the groupconsisting of capillary tubes, expansion valves, orifice restrictors andneedle valves.
 15. The method of operating the refrigerator applianceaccording to claim 10, wherein the valve system comprises a valve orvalves selected from the group consisting of a solenoid driven singleinlet and single outlet-type valve, a solenoid driven single inlet andat least one selectable outlet-type valve, and a stepper motor drivensingle inlet and at least one selectable output-type valve.
 16. Themethod of operating the refrigerator appliance according to claim 10,wherein the multi-capacity compressor is selected from the groupconsisting of a variable speed compressor, a variable capacitycompressor, a linear compressor and a two-speed compressor.
 17. Themethod of operating the refrigerator appliance according to claim 10,wherein the suction line heat exchanger is an intercooler in thermalcontact with the portion of the refrigerant circuit between thecondenser and the evaporator containing the primary pressure reducingdevice at a location downstream from the valve system and upstream fromthe primary pressure reduction device.
 18. The method of operating therefrigerator appliance according to claim 10, wherein the suction lineheat exchanger is in thermal contact with the primary pressure reducingdevice.